Probiotic Bacteria Counter Depression in Mice

A species of probiotic bacteria found in some yogurt reduces stress, anxiety, and depression in mice, finds a study published online this week in Proceedings of the National Academy of Sciences.

In the experiment, explains a report in Nature News, 16 healthy experimental mice were fed broth containing a strain of Lactobacillus rhamnosus and were then subjected to stress tests along with 20 healthy control mice that had been fed broth without the bacteria. While navigating a maze, the experimental mice showed greater tendency to go into open spaces, indicating that they were less anxious. When forced to swim, the experimental mice were more inclined than the control mice to struggle rather than give up.

After the stressful swim, the experimental mice had half as much of the stress hormone corticosterone as the control mice. In addition, the experimental mice had brain receptors for the neurotransmitter GABA arranged in a manner found in animals that are not depressed. When the scientists cut the vagus nerve (which carries communication between the brain and the guts) in the experimental mice, this rearrangement disappeared, indicating that the bacteria were responsible for the change.

Looking toward the future, probiotic bacteria may someday be able to play a role in reducing depression in people.

Sources

Probiotic bacteria lessens depression... [Press Release]

Friendly bacteria cheer up anxious mice [Nature News]

Ingestion of Lactobacillus strain regulates emotional behavior and central GABA receptor expression in a mouse via the vagus nerve (abstract) [Proceedings of the National Academy of Sciences]